Afshin Haghighat

Bio: Afshin Haghighat is an academic researcher from InterDigital, Inc.. The author has contributed to research in topics: Telecommunications link & Beamforming. The author has an hindex of 17, co-authored 72 publications receiving 2078 citations. Previous affiliations of Afshin Haghighat include Wilmington University & Sony Broadcast & Professional Research Laboratories.

Systems and methods for an enhanced control channel

Abstract: Methods and systems for sending and receiving an enhanced downlink control channel are disclosed. The method may include receiving control channel information via an enhanced control channel. The method may also include using the control channel information to receive a shared channel. The method may include detecting the presence of the enhanced control channel in a given subframe. The enhanced control channel may be transmitted over multiple antenna ports. For example, code divisional multiplexing and de-multiplexing and the use of common and UE-specific reference signals may be utilized. New control channel elements may be defined, and enhanced control channel state information (CSI) feedback may be utilized. The presence or absence of legacy control channels may affect the demodulation and or decoding methods. The method may be implemented at a WTRU.

Method and apparatus for random access in multicarrier wireless communications

Abstract: Methods and apparatus for random access in multicarrier wireless communications are disclosed. Methods and apparatus are provided for physical random access channel (PRACH) resource signaling, PRACH resource handling, preamble and PRACH resource selection, random access response (RAR) reception, preamble retransmission, and transmission and reception of subsequent messages. A method for maintaining an allowed multicarrier uplink (UL) random access channel (RACH) configuration set by adding an UL carrier to the allowed RACH configuration set provided that a triggering event occurs and performing a random access (RA) procedure using the allowed RACH configuration set. A method for sending data in multicarrier wireless communications by determining a set of available UL carriers and selecting an UL carrier from the set of available UL carriers.

On the Number of RF Chains and Phase Shifters, and Scheduling Design With Hybrid Analog–Digital Beamforming

Abstract: This paper considers hybrid beamforming (HB) for downlink multiuser massive multiple-input multiple-output (MIMO) systems with frequency selective channels. The proposed HB design employs sets of digitally controlled phase (fixed phase) paired phase shifters (PSs) and switches. For this system, first we determine the required number of radio frequency (RF) chains and PSs such that the proposed HB achieves the same performance as that of the digital beamforming (DB) which utilizes $N$ (number of transmitter antennas) RF chains. We show that the performance of the DB can be achieved with our HB just by utilizing $r_t$ RF chains and $2r_t(N-r_t + \text{1})$ PSs, where $r_t \leq N$ is the rank of the combined digital precoder matrices of all subcarriers. Second, we provide a simple and novel approach to reduce the number of PSs with only a negligible performance degradation. Numerical results reveal that only ${20}{-}{40}$ PSs per RF chain are sufficient for practically relevant parameter settings. Finally, for the scenario where the deployed number of RF chains $(N_a) $ is less than $r_t$ , we propose a simple user scheduling algorithm to select the best set of users in each subcarrier. Simulation results validate theoretical expressions, and demonstrate the superiority of the proposed HB design over the existing HB designs in both flat fading and frequency selective channels.

Method, system and apparatus for downlink shared channel reception in cooperative multipoint transmissions

Abstract: A method and apparatus may be used to enable reception of a downlink (DL) shared channel in a cooperative multipoint transmission (CoMP). The method and apparatus may determine whether CoMP is applied to a transmission. The method and apparatus may acquire other CoMP related information. The method and apparatus may apply to non-transparent CoMP scenarios.

Method and apparatus for contention-based uplink data transmission

Abstract: A method and apparatus for a wireless transmit receive unit (WTRU) to use a contention-based uplink communications channel, applies a rule-based restriction of access to the contention-based uplink channel that attempts to use at least one contention-free uplink channel allocation for uplink transmissions on a condition that at least one contention-free uplink channel allocation has been granted.

Hybrid Digital and Analog Beamforming Design for Large-Scale Antenna Arrays

Abstract: The potential of using of millimeter wave (mmWave) frequency for future wireless cellular communication systems has motivated the study of large-scale antenna arrays for achieving highly directional beamforming. However, the conventional fully digital beamforming methods which require one radio frequency (RF) chain per antenna element is not viable for large-scale antenna arrays due to the high cost and high power consumption of RF chain components in high frequencies. To address the challenge of this hardware limitation, this paper considers a hybrid beamforming architecture in which the overall beamformer consists of a low-dimensional digital beamformer followed by an RF beamformer implemented using analog phase shifters. Our aim is to show that such an architecture can approach the performance of a fully digital scheme with much fewer number of RF chains. Specifically, this paper establishes that if the number of RF chains is twice the total number of data streams, the hybrid beamforming structure can realize any fully digital beamformer exactly, regardless of the number of antenna elements. For cases with fewer number of RF chains, this paper further considers the hybrid beamforming design problem for both the transmission scenario of a point-to-point multiple-input multiple-output (MIMO) system and a downlink multi-user multiple-input single-output (MU-MISO) system. For each scenario, we propose a heuristic hybrid beamforming design that achieves a performance close to the performance of the fully digital beamforming baseline. Finally, the proposed algorithms are modified for the more practical setting in which only finite resolution phase shifters are available. Numerical simulations show that the proposed schemes are effective even when phase shifters with very low resolution are used.

Multibeam Antenna Technologies for 5G Wireless Communications

Abstract: With the demanding system requirements for the fifth-generation (5G) wireless communications and the severe spectrum shortage at conventional cellular frequencies, multibeam antenna systems operating in the millimeter-wave frequency bands have attracted a lot of research interest and have been actively investigated. They represent the key antenna technology for supporting a high data transmission rate, an improved signal-to-interference-plus-noise ratio, an increased spectral and energy efficiency, and versatile beam shaping, thereby holding a great promise in serving as the critical infrastructure for enabling beamforming and massive multiple-input multiple-output (MIMO) that boost the 5G. This paper provides an overview of the existing multibeam antenna technologies which include the passive multibeam antennas (MBAs) based on quasi-optical components and beamforming circuits, multibeam phased-array antennas enabled by various phase-shifting methods, and digital MBAs with different system architectures. Specifically, their principles of operation, design, and implementation, as well as a number of illustrative application examples are reviewed. Finally, the suitability of these MBAs for the future 5G massive MIMO wireless systems as well as the associated challenges is discussed.

User terminal, radio base station and radio communication method

Abstract: The present invention is designed to provide a user terminal, a radio base station and a radio communication method of novel structures that can achieve a good communication environment. A radio base station non-orthogonal-multiplexes downlink signals for a plurality of user terminals over a given radio resource, a user terminal having received the downlink signals for the plurality of user terminals decodes downlink signal for another user terminal, judges whether or not the downlink signal for the other user terminal has been successfully received, based on the decoding result of the downlink signal, reports a judgement result as to whether or not the downlink signal for the other user terminal has been successfully received and a judgement result as to whether or not a downlink signal for the user terminal has been successfully received, to the radio base station, and then the radio base station executes retransmission control of downlink signals based on reports from the user terminal.

Telecommunications apparatus and methods

Abstract: A wireless telecommunication system comprises base stations for communicating with terminal devices. One or more base stations support a power boost operating mode in which a base station's available transmission power is concentrated in a subset of its available transmission resources to provide enhanced transmission powers as compared to transmission powers on these transmission resources when the base station is not operating in the power boost mode. A base station establishes an extent to which one or more base stations in the wireless telecommunications system support the power boost operating mode conveys an indication of this to a terminal device. The terminal device receives the indication and uses the corresponding information to control its acquisition of a base station of the wireless telecommunication system, for example by taking account of which base stations support power boosting and/or when power boosting is supported during a cell attach procedure.

Mobile communication method and radio base station

Abstract: In a mobile communication method by which a mobile station (UE) transmits a control signal to a radio base station (eNB) in an uplink by using an uplink dedicated resource, different methods for determining whether or not a synchronization state is established in the uplink, are used depending on whether or not the uplink dedicated resource is set up.